The present disclosure relates generally to an intravascular catheter and to a method for using an intravascular catheter for modeling the geometry of blood vessels.
Cardiovascular Disease is a leading health problem in the developed world, with Coronary Artery Disease (CAD) being a particularly important problem. CAD typically occurs when part of the smooth, elastic lining inside a coronary artery becomes hardened, stiffened, and swollen with plaque. Plaque typically consists of calcium deposits, fatty deposits, and abnormal inflammatory cells. The formation of a plaque is termed Atherosclerosis. This plaque can cause an obstruction to the supply of oxygenated blood to the heart muscle and can cause chest pain (angina), and ultimately lead to heart attack and death.
The field of Interventional Cardiology is a branch of cardiology that deals specifically with catheter based treatments of structural heart diseases such as CAD. During a procedure known as Percutaneous Coronary Intervention (PCI) a catheter is inserted into a major systemic artery in either the groin or the arm and guided towards the entrance to the coronary tree. This catheter takes the form of a thin tube, through which a radio-opaque dye may be delivered into the bloodstream, allowing for visualization of the coronary arteries using a special type of X-ray imaging called Fluoroscopy.
If the vessel narrowing is deemed severe enough, a common treatment is the insertion of a stent to increase the diameter of the artery. To place the stent, another catheter is threaded through the blood vessels via a guidewire into the heart where the coronary artery is narrowed by plaque. When the catheter is in place, a balloon tip covered with a stent is inflated. The balloon tip compresses the plaque and expands the stent. Once the plaque is compressed and the stent is in place, the balloon is deflated and withdrawn with the catheter. The stent stays in the artery, holding the artery open. If the stent is not aligned correctly with the walls of the artery, termed incomplete stent apposition (ISA), there is an increased risk of long term negative outcomes such as myocardial infarction and stent thrombosis.
One of the challenges in this field is accurately assessing the state of disease in a patient's coronary arteries. Coronary angiograms are commonly used by clinicians to manually identify and quantify the degree of a stenosis, wherever they may appear. Given an angiogram's finite resolution, the fact that they are 2D projections of a complex three-dimensional (3D) structure, and the fact that a stenosis can reduce the amount of contrast agent flowing through a stenosis, reducing its visibility, has meant that in many cases other catheter based imaging techniques are used. These techniques include Intravascular Ultrasound (IVUS) or Intravascular Optical Coherence Tomgraphy (OCT), that acquire images of an artery and stenosis from the interior of the artery using an imaging sensor located at the catheter tip. Although these modalities provide much higher resolution images of the interior of an artery, they do not acquire any information about the 3D position and orientation of the catheter tip while the images are being acquired (e.g., if an OCT dataset is acquired while retracting the imaging sensor through a tortuous curved arterial branch, this could not be ascertained by examining the images).